Social participation has been linked to healthy aging, yet little is known about social participation during extended periods of time for adults with intellectual and developmental disabilities. The social participation of 777 adults with intellectual and developmental disabilities (aged 18-77 years), during a 4-year period, was examined. Sociodemographic, physical, and behavioral health-related correlates of engagement in social participation were investigated. Findings indicated that the majority of adults with intellectual and developmental disabilities engaged in at least a moderate level of social participation during the 4-years. Employment status, physical health, and Special Olympics participation were associated with a higher level of social participation. Findings have implications for supports and services seeking to promote social participation opportunities for adults with intellectual and developmental disabilities.